It is known in the art to use night vision systems to allow the driving of vehicles at night and under adverse weather conditions. One such night vision system, known as a Driver's Vision Enhancer (DVE) is described in U.S. Pat. No. 6,521,892 to Emanuel et al. The Emanuel DVE consists of a forward-looking thermal imager, also known as a Sensor Module (SM), for acquiring thermal radiation from a viewed scene and a Display and Control Module for displaying a visible image of the scene to the driver.
The portion of the scene called the Field of View can be acquired at any time and is expressed in elevation and azimuth angles. Such DVE systems are also equipped with mechanisms allowing the user to rotate the optical axis of the SM in elevation and azimuth to allow acquisition of the scene beyond the limits of the Field of View. The total scene area viewable by the DVE system is called the Field of Regard (FOR). The FOR includes the FOV and is frequently larger than the FOV, i.e., a non-movable DVE has a fixed FOR and FOV covering the same azimuth and elevation. For example, U.S. Pat. No. 6,563,102 to Wrobel et al. describes a FOR mechanism useable with the Emanuel DVE system described above.
Existing techniques for rotating the optical axis of the SM include rotating the SM itself in both azimuth and elevation, e.g., as used in the Wrobel patent, and rotating the associated folding mirror for vertical FOR and rotating the SM itself for the horizontal FOR, e.g., as used in DVE systems having periscopic optics having a vertical optical axis.
Several techniques can be used to rotate the optical axis of the Sensor Module. The one described in the aforementioned patent uses the rotation of the Sensor Module itself in both azimuth and elevation. DVE systems using periscopic optics (vertical optical axis) use the rotation of an associated folding mirror to provide vertical FOR and use the rotation of the SM itself for the horizontal FOR.
In order to utilize a mirror in the periscopic DVE systems, an entrance window is positioned in front of the mirror to prevent dust and contaminants from reaching the mirror. A lens assembly positioned to receive light from the mirror directs an image to a radiation detector for processing and ultimately display to a user. In operation, light from a viewed scene passes through the entrance window, reflects off the mirror, and passes through the lens assembly to the radiation detector. A reduction in light received from a viewed scene occurs as the light passes through the multiple components of the folding mirror mechanism.
There is a need in the art for an alternate FOR mechanism and associated SM packaging, which is applicable to forward looking DVE systems. Further, there is a need in the art for such a system that is improved in terms of simplicity, cost, and performance.